Just a week ago, the actor posted an Instagram pic of Joshua, wishing his son a happy birthday with a super sweet message.

"Nothing like having a much-improved 2.0 version of yourself around to remind you just how much better you can be," Van Der Beek wrote. "Happy 4th birthday to my guy... As sensitive as he is strong, as soulful as he is playful... And the kid know how to time a jump for a picture #BirdsInTheBackground #HesANatural ? Love you beyond, bud."